I have the setting as follow:

real_ip_header proxy_protocol;
real_ip_recursive on;
set_real_ip_from 192.168.1.0/24;

For example, when I send request to nginx from 10.0.0.1, $proxy_protocol_addr prints 10.0.0.1, which is the original client, but $remote_addr prints 192.168.1.1 which is our proxy.